In a previous article, I introduced some simple catch basins and their applications in yard and residential roof downspout drainage. Products by National Diversified Systems (NDS) were presented. In this article, we will look at downspout catch basin installation and highlight two square NDS catch basins.

Catch Basins and Water Quality

 I like to think of a catch basin as the “first line of defense” in cleaning up rain water and drainage pipes. It is common for homeowners to put their downspout water into a pipe that then travels out to the street or a back yard location. This often leads to clogged drainage pipes. Over time, leaves, sticks and sand particulate from roofing shingles will build up in the pipe to gradually reduce drainage efficiency. A catch basin helps to reduce this problem in two ways. First, the grating that covers the basin filters out the coarse debris that finds its way through the downspout, thus “catching” the biggest contributing factor to clogged drain pipes.

The second way of cleaning the water is the catch basin sump. Finer particles that pass the grating are “caught” in the sump portion of the basin. The sump is a small water reserve that is just below the exit pipe (invert out) of the basin. As suspended particles are first entering the basin, they must pass a swimming test. If they are able to enter the sump portion of the basin and “float with the current” to the exit pipe, they win. If they are too heavy or the water is too slow, they will sink to the bottom of the sump and be left there for later removal. The particles that generally “pass” the sump test are light organics and fine silt and clay sized. The particles that get trapped in the sump need to be cleaned out periodically. (So, check your sumps!!) Also, the deeper or wider the sump, the more difficult it will be for the particle to “swim” to the exit pipe.

Catch Basin Installation

That’s the theory. Let’s talk about installation. I’m going to show two methods that involve installing catch basins in concrete: the Single pour and the Double pour methods. I always like to place drainage products in concrete because of a number of reasons.
1) It adds strength to the drain, especially if it is made of plastic,
2) It anchors the drainage product to the ground and reduces “floating”,
3) I like the look of a concrete apron around the drain and feel that it helps direct the water to the drain,
4) And lastly, I like working with concrete.

Single Pour Method

The single pour method involves setting a catch basin in a form and making a single concrete pour to form the casing. For demonstration purposes, I’m using a NDS 900 Catch basin with a single outlet. The 900 series catch basin is a 9” x 9” basin with a built in 2 inch sump. When you order this basin, you need to know what pipe size you are using to evacuate the water because you will have to order a pipe adapter to insert into the outlet of the basin. (Note: all larger NDS catch basins will have this feature.)

Basin Install Hole

The next step requires setting the basin, connecting the pipe to the drain and building a wooden mold that will form the concrete casing. I was sloppy with this installation. I admit it. Normally, my work has symmetry. In this case, I never centered the basin properly within the mold. But, you will see soon that this can be made to look good. You can see that I used metal “pins” (or spikes) that were hammered into the ground which hold the wooden form into place. The pins have holes in them which allow me to hammer nails through them and into the wooden form. This is how the mold is held rigid against the earth. Also, the inside of the mold was lubricated with an oil to help in the release of the mold from the hardened concrete. Many products are available on the market to provide this release. However, an oil and kerosene mixture will work, as well as, plain ol’ Vaseline.

Pouring the concrete in the mold is the next step. I used a 50 pound sack of concrete purchased from a local home improvement store. After mixing to the proper consistency, I placed the concrete in the mold and used a metal rod to poke the wet mixture and ensure that air bubbles were not trapped. I want to point out here that I didn’t have concrete under the catch basin. I actually had a large stone. The purpose of the concrete was to provide a “shell” around the catch basin which could provide additional drainage surface for downspout water to collect prior to entering the basin.

Basin Install Pour

 I stripped the mold after I let the concrete set over night. I trimmed away all tramp rock, dirt and wood to leave behind a clean, crisp concrete cube. I want to point out here that I centered the drain under the downspout. And, because the downspout pipe was so close to the wall, I opted to rest the catch basin against the house. I could have put a curved spout on the downspout and brought the catch basin 3 inches away from the wall. In this case, I would have had a concrete section between the house and the catch basin. Perfect symmetry would have been achieved!!! (I should have done that.)

Basin Install Stripped

 Next, I made it look purdy! (Some people would prefer “pretty”.) I packed clean soil around the concrete. I put a bead of caulking between the wall and the concrete casing to keep water away from that spot. I added a little downspout extension to accurately direct the water. And, I mulched the area. Doesn’t it look nice? Even with the poor symmetry of the concrete, it looks charming. Even still, I learned from this experience and I will do a better job on the next installation.

Final Basin

 Double Pour Method

The double pour catch basin installation method utilizes two concrete pours to set the drain. The first pour is made around the drain to stabilize it, and the second pour, made after the first has hardened, is to complete construction of the larger drainage surface.

The double pour method is generally used when you are placing the drain within a large open area or within a larger form. For instance, if you are making a new concrete driveway, there will be forms defining the edges of the driveway. It would be unnecessary to build a perimeter form around your catch basin or driveway drain. You would merely set your drain in a location at an elevation that would facilitate the drainage of the driveway. And, after setting up the drain pipes and any structural steel, the whole driveway would be poured at the same time.

However, a catch basin will try to rise out of the wet concrete as would a boat on water. Lightweight objects will become buoyant and sway or float due during concrete placement if not locked down. A small amount of concrete poured at the base of the drain will provide the stability needed for the final pour. And prior to drying, the elevation and alignment can be “fine tuned” in preparation of the final pour.

In the example that follows, I used a 12” x 12” catch basin made by NDS. This product, NGB1200, is promoted as the Next Generation Basin. Its walls are constructed in a manner which allows you to adjust the depth of the sump area at the base of the basin. Walls are constructed either with an invert opening or with a solid wall. The following picture shows installing and trimming a solid wall section of the basin.

Install Closed End

 For this installation, I decided to have a shallow sump. When installing the open invert wall section, I trimmed the section to give only a 1” deep sump. A pipe adapter was required for me to attach my 4 “ S&D pipe. This NDS fitting (#1243) locked into the side of the open basin wall.

Install Open End

 This basin was to be placed at the base of a downspout adjacent to a driveway. The drain was to become a part of a new sidewalk next to the driveway and house. A hole was prepared to the proper depth. The existing driveway and house foundation formed borders that flanked the drain.

Install Hole

 Next, a small amount of concrete was placed in the hole. The catch basin was set in the hole and filled with stones to help keep it from floating. More concrete was poured around the basin to ensure that it would be locked into place once dried. While the concrete was still wet, the basin was adjusted to the proper elevation and symmetry with the driveway and house.

Install 1st Pour

 After the first pour had hardened, it was time to pour the sidewalk. The stones that were originally put in the catch basin to stabilize it were left in place during the 2nd pour. Once the sidewalk had been poured and was dry enough to walk on, the stones were removed and the catch basin was cleaned of stray concrete. As a final touch, a cast iron “Sun Grate” by Ironage Designs was then installed to complete the project.

Sungrate Installed

 Final Notes

Catch Basin sizes and styles vary with application and drainage requirements. Residential catch basin range in size from 6” diameter garden drains to 24” x 24” yard drains. A wide variety of grating options are available. Plastic, brass, cast iron and chrome grates are designed to meet the cost or aesthetic requirements of your drainage project.

Trenchdrain.biz is an authorized dealer for NDS drainage products and can offer advice in making catch basin selections. In addition, we carry Ironage decorative grating products that fit many of the NDS drainage products.

 Contact at 610-638-1221 or email Trenchdrain.biz